1. Field of the Invention
The present invention relates generally to a polymer processing technique, and more particularly to a pressure-controlling foam molding method and a device thereof.
2. Description of the Related Art
Taiwanese Patent Application No. 09219239 discloses a pressure-controlling foam molding method. Taiwanese Patent Application No. 092206257 discloses a pressure-controlling foam molding device. The above patents provide an out-mold polymer foam processing technique. According to this technique, the environmental pressure condition is controlled to change the polymer foam molding process. To speak more specifically, in the technique provided by the above patents, a blank mold for molding a foam blank and a shaping mold for molding a product are side by side arranged in a closed pressure room. By means of an external pressure controlling mechanism, the internal environmental pressure of the pressure room can be changed. After the polymer material is molded into a blank by the blank mold, the blank mold is opened under a specific pressure environment provided by the pressure room. Then the molded blank is moved from the blank mold into the shaping mold within the same pressure room to perform shaping process for the blank.
Substantially, in the technique provided by the above patents, an operable transfer unit is disposed between the blank mold and shaping mold. After the blank mold is opened under the specific pressure environment, a sucker of the transfer unit sucks the blank in the blank mold. Then the transfer unit operates to move the sucked blank to the shaping mold beside the blank mold. According to the above, the blank transfer process substantially includes three steps of: first using the sucker to suck the blank and moving the blank upward from the blank mold; then horizontally transversely moving the blank to an upper side of the shaping mold in an opened state; and finally moving the blank downward and filling the blank into the mold pit of the shaping mold in an opened state.
In the technique provided by the above patents, the blank mold and the shaping mold are side by side arranged so that the blank must be transferred in the above manner. In order to ensure that the blank can be successfully filled into the mold pit of the shaping mold, a specific high pressure is applied to the blank for limiting the extent to which the blank foams. Under such circumstance, during transfer, the volume of the blank is much smaller than the capacity of the mold pit of the shaping mold, into which the blank is to be filled. Accordingly, with sufficient room in the mold pit of the shaping mold, even if the blank is displaced during transfer, the blank can be still successfully filled into the mold pit of the shaping mold. After the blank is filled into the shaping mold and the shaping mold is closed, the high pressure is relieved to foam the blank in the closed mold cavity of the shaping mold.
The above technique is applicable in the field of foam molding. However, during transfer of the blank, it is necessary to limit the extent to which the blank foams. Therefore, it is necessary to provide a high air pressure in the pressure room. The higher the air pressure value is, the larger the energy consumption is. As a result, much energy is wasted. Moreover, during transfer of the blank, the blank is permitted to slightly displace. However, the blank is first moved upward and then transversely moved and finally lowered. That is, the blank is moved in multiple directions during transfer. In this case, it is hard to control the possible displacement of the blank during transfer. As a result, it often takes place that the blank is over-displaced and fails to be filled into the shaping mold.